Power supply tends to be diversified in such a manner that renewable energy such as sunlight and wind power is combined with conventional power generation such as nuclear power and thermal power. In order to stabilize power quality when the diversified power supply is used, it has been proposed to build a next-generation power grid (smart grid). In the next-generation power grid, power management needs to be performed by installing a smart meter (hereinafter also referred to as SM) configured to add up power consumptions and a home server configured to manage electrical equipment in every home and office. In addition, a meter data management system (hereinafter also referred to as MDMS) and an energy management system (hereinafter also referred to as EMS) connected to smart meters via the next-generation power grid perform management of power used in homes and offices and control for power supply to homes and offices.
For example, a smart meter communicates with the meter data management system to transmit a power consumption of a home or an office thereto. The meter data management system then stores and manages power consumptions transmitted from smart meters of homes and offices at regular time intervals. The energy management system performs power control including requesting the smart meters or the home servers of homes and offices to reduce power consumptions and charging and discharging of storage batteries connected to the next-generation power grid based on power consumptions of homes and offices stored in the meter data management system.
Moreover, it has been proposed to provide various services by using power consumptions managed by the meter data management system. Provision of such services can be realized by connecting an application server on which various applications are installed to the next-generation power grid. Examples of such application server include a billing server managed by a provider. Such a billing server performs billing processes based on power consumptions of homes and offices managed by the meter data management system.
Power consumptions managed by the meter data management system can be transmitted to the smart meters upon request. For example, upon receipt of a request for accessing power consumptions from a smart meter, the meter data management system can disclose information such as power consumptions managed by the meter data management system.
However, when power consumptions of homes and offices are managed using storage devices included in the meter data management system, an administrator of the meter data management system or an unauthorized third party breaking into the meter data management system can access the power consumptions of homes and offices. If the administrator or the unauthorized third party accesses the power consumptions, he/she can guess whether or not there is someone at home or office, activities of people therein or the like. As a result, privacy concerns arise.